A box with four external cable clamps contributes how many additional conductors to the fill allowance?

When determining the fill allowance for conduits and boxes in electrical installations, external cable clamps play a specific role. In this scenario, external cable clamps do not count towards the calculation of additional conductors in terms of fill capacity.

The National Electrical Code (NEC) specifies that additional conductors are counted based on the conductors themselves, not on the external clamps or fittings attached to a box. Since the clamps are intended for securing cables and do not occupy space within the box, no additional conductors are added to the fill calculation due to the presence of these clamps.

Thus, if a box has four external cable clamps, it contributes zero additional conductors to the fill allowance. This adheres to the guidelines set by the NEC regarding box fill calculations and maintains safety and code compliance in electrical installations.